PathingPolygon.js

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************************************************************************
Author: Donald Beals
Description: The PathingPolygon class, which is used to house the polygon
 * and generate the pathing grid.
****************************** Change Log ******************************
4/26/2015 4:24:47 PM - Created initial file. (dbeals)
***********************************************************************/
function PathingPolygon() {
	this.points = new Array();
	this.nodes = new Array();
	this.nodeWidth = 16;
	this.nodeHeight = 16;
	this.width = 0;
	this.height = 0;
	this.isClosed = false;
	this.useTightTests = true;

	function isPointInsidePolygon(points, testX, testY) {
		var counter = 0;
		var point1 = points[0];
		for(var index = 1; index <= points.length; ++index) {
			var point2 = points[index % points.length];
			if(testY > Math.min(point1.y, point2.y) &&
				testY <= Math.max(point1.y, point2.y) &&
				testX <= Math.max(point1.x, point2.x) &&
				point1.y != point2.y) {
				var xinters = (testY - point1.y) * (point2.x - point1.x) / (point2.y - point1.y) + point1.x;
				if(point1.x == point2.x || testX <= xinters)
					++counter;
			}
			point1 = point2;
		}
		return counter % 2 != 0;
	}

	function isRectangleInsidePolygon(points, node, tightTest) {
		var leftTopRightBottom = isPointInsidePolygon(points, node.x, node.y) && isPointInsidePolygon(points, node.x + node.width, node.y + node.height);
		var rightTopLeftBottom = isPointInsidePolygon(points, node.x + node.width, node.y) && isPointInsidePolygon(points, node.x, node.y + node.height);

		if(tightTest)
			return leftTopRightBottom && rightTopLeftBottom;
		return leftTopRightBottom || rightTopLeftBottom;
	}

	this.close = function() {
		var firstPoint = this.points[0];
		var lastPoint = this.points[this.points.length - 1];
		if(lastPoint.x != firstPoint.x || lastPoint.y != firstPoint.y)
			this.points.push(firstPoint);
		this.isClosed = true;
	}

	this.clear = function() {
		this.width = 0;
		this.height = 0;
		this.nodeWidth = 16;
		this.nodeHeight = 16;
		this.nodes = new Array();
		this.points.clear();
		this.isClosed = false;
	}

	this.createGrid = function(nodeWidth, nodeHeight) {
		var minX = Number.MAX_VALUE;
		var minY = Number.MAX_VALUE;
		var maxX = Number.MIN_VALUE;
		var maxY = Number.MIN_VALUE;

		for(var index = 0; index < this.points.length; ++index) {
			var point = this.points[index];
			if(point.x < minX)
				minX = point.x;
			if(point.y < minY)
				minY = point.y;
			if(point.x > maxX)
				maxX = point.x;
			if(point.y > maxY)
				maxY = point.y;
		}

		var bounds = {
			x: minX,
			y: minY,
			width: maxX - minX,
			height: maxY - minY,
		};

		this.width = Math.ceil(bounds.width / nodeWidth);
		this.height = Math.ceil(bounds.height / nodeHeight);

		var output = new Array(this.width * this.height);
		for(var row = 0; row < this.height; ++row) {
			for(var column = 0; column < this.width; ++column) {
				var nodeBounds = {
					x: bounds.x + (column * nodeWidth),
					y: bounds.y + (row * nodeHeight),
					width: nodeWidth,
					height: nodeHeight
				};

				output[(row * this.width) + column] = {
					column: column,
					row: row,
					bounds: nodeBounds,
					isPathable: isRectangleInsidePolygon(this.points, nodeBounds, this.useTightTests),
				};

			}
		}
		this.nodes = output;
	}

	this.getNodeAtXY = function(x, y) {
		for(var index = 0; index < this.nodes.length; ++index) {
			var node = this.nodes[index];
			var left = node.x;
			var top = node.y;
			var right = node.x + node.width;
			var bottom = node.y + node.height;

			if(x >= left && y >= top && x < right && y < bottom)
				return node;
		}
		return {
			column: -1,
			row: -1,
			bounds: {
				x: 0,
				y: 0,
				width: 0,
				height: 0,
			},
			isPathable: false,
		};
	}

	this.getNodeAtColumnRow = function(column, row) {
		return this.nodes[(row * this.width) + column];
	}
	
	this.containsColumnRow = function(column, row) {
		return column >= 0 && column <= this.width && row >= 0 && row <= this.height;
	}
	
	this.debugDraw = function(drawLine, drawNode) {
		if(drawNode != null && this.isClosed) {
			for(var index = 0; index < this.nodes.length; ++index) {
				var node = this.nodes[index];
				if(!node.isPathable)
					continue;
				drawNode(node);
			}
		}
		
		if(drawLine != null && this.points.length > 1) {
			for(var index = 0; index < this.points.length - 1; ++index) {
				var start = this.points[index];
				var end = this.points[index + 1];
				drawLine(start, end, index);
			}
		}
	}
}